Adhesive and process of making same



Patented Oct. 9, 1934 PATENT orrlca 1,976,436 Anrmsrvn AND rnooess orMAKING SAME Charles N. Cone, Seattle, wash, asslgnor to I. F. Laucks,Inc., Seattle, Wash, a corporation of Washington No Drawing. ApplicationNovember-6, 1931,

Serial No. 573,516

22 claims.

My invention relates to the process of making a laminated constructionunit, the laminated product of said process, the process of making theadhesive for such unit and the adhesive product,

of said last process;

More particularly, my invention relates to a new laminated constructionunit characterized by its exceedingly high water and weatherresistingproperties, and byits being cold pressed for the w initialsetting of the glue binder for the plies and then its being heatedwithout pressure to increase the water resistance; and my inventionrelates to the process of treating blood to serve as the glue baseforthe binder of the plies of such unit and to the blood glue compositionas a whole.

While it has'been known for a long time that blood, the form of a wetglue, when hot pressed made a highly water resistant construction unit,nevertheless, the hot press with wet glues has so many seriousdisadvantages in practice that its use is exceedngly limited and rare inAmerican plywood plants. In fact, its use with wet glues is so limitedthat for-practical purposes, it can be said to be scarcely used at allin the United States for the manufacturing of plywood. The

hot press, besides being of itself exceedingly expensive, does not lenditself to economical large scale production, for among other reasons,too much of the press opening is occupied with the press members. Hotpressing is expensive and cumbersome and is limited to stock sizes ofpanels, being uneconomical and inconvenient t6 use when making panels ofvaried sizes.- There have also been proposals'to first cold press bloodglued plywood panels, and then follow this with a hot pressing. This, ofcourse, has all the disadvantages of hot pressing, coupled with theextra expense of cold pressing.

A primary object of my invention is to eliminate 4c the hot press inmaking laminated products with a dispersed blood glue, and still obtainthe high water resistance which is a concomitant of a heated blood glueline.

By far the greatest part of total amount of plywood laid up today in theUnited States is composed of coniferouswoods as, for example, fir, pine,etc. However, heretofore, hot pressing with wet blood glue has not beenadaptable to the manufacture of plywoodfrom coniferous woods becausethese woods do not have sap vessels, nor do they have'any ducts or cellsof sufllcient length to permit escape of moisture during hot pressing,there by resulting in severe checking and blistering of the faces. Aprimary object o! my invention, or discovery, is to make the'waterresistant properthe shear test after soaking forty-eight hours-in water,as well as the ability of the panels to remain sound during soaking inwater for months.

Also serious objection obtains to the process followed in themanufacture of blood glued plywood in that it is quite impossible tocontrol the moisture content of the plywood panel when the hot press isused, and as a result the great difliculty of blistering is encountered,i. e., the bulging out of areas due to internal steam pressure oftrapped moisture. Also, there is the necessity to dry out or season thepanel after removal from the hot press as heretofore employed. A primaryobject of my invention is to overcome this objection and to provide aplywood blood glued panel of exceedingly high dry strength and highwater resistance, in which the moisture content is controllable so thatsubsequent seasoning is obviated. It is to be understood that myinvention is applicable not only to plywood, but other materialssuitable for lamination, such as cellulose containing compositionboards, etc.

Blood glue as heretofore commonly spread Q gether, so that the panel canbe handled and subjected to a nibsequent heating operation in theabsence of pressure without damage. In provid- 10o .ing such a bloodbase glue, my invention goes directly contrary to prior teachingin thatinstead or no alkalinity, or very low alkalinity, I find in my new bloodbase glueand processes, that a positive alkalinity is essential toobtain the necessary invenprotein, which'samejma'ybe thus used toconstitute a considerable percentage, even seventyfive percent of thebase of the glue used in my process, as well as by the fact that thewater requirement is increased by using proper percentage of alkalinity.My discovery includes the fact,

that with such degree of alkalinity as will'give the necessary waterrequirement toprovide an economical spread, nevertheless the initial setin the cold press is of suflicient strength to hold the plies withoutpressure against the stresses developed during heating and that suchalkalinity does not prevent the heating step imparting the necessarywater resistance. Also my discovery includes the fact that such initialsetting does not prevent the development of water resistance in the glueupon subsequent heating.

Finally, a primary purpose of my invention is to make a plywood productas characterized by the properties above set forth which can be rapidlyproduced in large scale production and at greatly reduced cost.

These objects are achieved by my invention or discoveries which willnext be fully set forth. Before giving the details the invention will beset forth in a summary manner.

Briefly, therefore incompletely stated, my invention or discoverycomprises that blood can be treated as the base of an adhesive or glue,or as the critical portion of the base, with chemicals which impart apositive and essential alkalinity so as to make a glue which, whenspread by means of the usual mechanical rollers and laid up to form apanel and cold pressed as usual as one member of a rack of panels, willhave the requisite dry' strength and sufficient adhesion to hold theplies, despite the severe strains developed when the moisture content ofthe panel changes during the next following step. Then, the panel isheated without pressure, (i. e., without using a hot press), the heatbeing sufficient, about 212 F., to so act on the blood as to give a veryunexpected increase in wet strength, and usually some increase in drystrength. Instead of a mild or no alkalinity, my adhesive compositioncomprises the reaction products of blood and alkalinity producingchemicals of 3% to 20% of the glue base, besides lime and solublesilicate salts in some formulae, and as a foam eliminating agentterpineol. The panel thus produced by this process and by means of thisadhesive, results in a panel practically waterproof and weatherresistant so as to be useful for outdoor purposes in contrast to theindoor use of plywood generally at the present time.

While a high water resistance is obtained even in the unheated panelsand While highly water resistant glues have been known before, I believethat this new discovery of mine enables the mak- 1 ing of a differentcharacter of plywood than has been heretofore known certainly at leastwith coniferous Woods, namely, that it has such properties that willenable plywood made by the use of my glue and process to withstand theaction of moisture indefinitely. While the commonly used shear strengthtest on plywood after soaking for 48 hours gives very high figures onplywood glued with this new glue, the same may also be true of otherglues, but I have found by practical tests such as weathering tests,exposure to the elements, repeated alternate soaking and drying tests,long continued soaking tests, freezing tests and alternate heating andsoaking tests, that plywood made by my process and glue withstands thesepractical tests and is for all practical purtests is a thing'which'isnotdetermined b'y'the ordinary wet shear test and it is in thisendurance to these practical tests that I consider that my "process andglue give new, unique and very valuable practical results forplywood.Prior known glues, even' though giving high wet shear tests, havesuffered a deterioration in strength when exposed to moisture or weatherfor some time and for this reason such panels have not been of practicaluse foroutdoor purposes.

After the cold pressing of the plywood, the panels contain aconsiderable percentage of moisture, and when such moist panels areheated a very severe strain is set up. Published figures show that thetransverse strains set up in even the weakest native woods during changeof moisture content amount to over 200 pounds per square inch. To holdthe panels during this second operation, that is, heating, it isnecessary that the glue line be strong enough to withstand this severestrain, and to make finally a panel without pressure which willbestronger than the unheated panel, requires a glue which will increasein strength during heating, such increase being greater than the strainset up.

When plywood is to be hot pressed, using a blood-base glue, a low degreeof alkalinity heretofore has been used or even no alkalinity at all.Thus ammonia, or small amounts of alkaline salts such as sodiumsilicate, or very small percentages of caustic soda will furnishsuflicient alkalinity for hot pressing. The case is radically differenthowever, in my process. I must use a positive alkalinity to secure thenecessary adhesion in the cold press, so that the cold pressed panelswill withstand the after heating operation.

To secure this positive alkalinity I prefer to use caustic soda as such,and in amounts over 3% referred to the adhesive base. When thus usingcaustic soda as such I am free from all the uncertainties of producingcaustic soda by double decomposition chemicals. (By double decom-'position I mean whatever reaction takes place in an aqueous colloidaldispersion of proteinous substances and other colloids, between lime andsodium salts such as sodium fluoride, sodium silicate, etc.)

While I prefer to use caustic soda as such, I find that I can get goodresults by using double decomposition chemicals such as the ones named,and I consider, in this invention, the combinations lime and sodiumsilicate, lime and sodium fluoride, etc. the equivalents, so far asalkalinity is concerned, of caustic soda as such, with this reservationhowever, which I can best explain by an example, viz: Sodium fluoridehas a molecular weight of 42, and by reaction with excess lime in water(i. e., in the absence of colloids) 42 parts sodium' fluoride will givetheoretically 40 parts caustic soda. The case is entirely different,however, in the presence of colloids. find that a combination of excesslime and 42 parts sodium fluoride is nowhere near as effective for mypurpose as 40 parts caustic soda as such. Furthermore, the effectivenessof double decomposition combinations varies greatly with the kind ofsodium salt used, so that in general I consider that a doubledecomposition combination for my purposes is less than as effec- In suchcase I ,poses waterproof. "Endurance to these practical nova-res i to bemarketed in sacks as a glue composition, for

example lime, sodium metasilicate and the chemicals which react to formcaustic soda by double decomposition in aqueous medium, and terpin'eol.

In general I find best resultswhen using from 8% to 15% caustic soda assuch, (i. e., 8% to 15% of thedry adhesive base) or correspondinglylarger amount of double decomposition chemicals. Above 20% caustic sodaas such I find that deterioration sets in, so that I consider 20% theupper limit.

Along with caustic soda I prefer also to use lime as 'I find that thisincreases the water resistance, 'and in some formula: also the drystrength. or course when using double decomposition combinations, limeis present, and in such case I prefer to add an excess of lime, by

which I mean an excess over the amountthat would be theoreticallyrequired to combine with whatever sodium salt or potassium salt is used,in the absence of colloids. I find that lime in amount of 7% givesexcellent results, while 15% I also gives very good water resistance.

When I use lime, I also may use sodium silicate to give increased waterresistance, e. g.,'30% water glass with 7% lime gives very great waterresistance, To a certain extent the combination lime plus sodiumsilicate may substitute for caustic soda. That is, when I use thiscombination, I may not use as much caustic soda as I would without thecombination. Silicate thus plays a dual role. e

In carrying out my invention, or discoveries, I

have developed many formulae of which examples .will be set forth withactual experimental tests,

results and explanation. A typical formula with blood is as follows:

; Parts I. Dried bloo 100 NaOH 8 Lime '7 Sodium silicate 30 Water 675 to725 When this is spread using 18 lbs. of dried blood per thousand squarefeet of plywood, three-ply i. e., two glue lines with 10 minutes time ofassem- -bly and pressed cold with 150 pounds pressure,

with inch fir plywood, it gives a dry strength of 283 and a. wetstrength of 243.

.After they are removed from the'press, I- then place the panels in anyconvenient apparatus forheating. This may be,'for example,.a veneerdryer, as used for drying the single plies, or better still a tunneldrier such as used for redrying panels. The panels may even be placed inracks in a hot room. By whatever means is used for the heating, I bringthe glue line to a temperature .of approximately 212 F. and 'hold it atthis temready to use without further seasoning. Because of the high, drystrength of the bond before heating, I run no risk of blistering,'whichis one of the disadvantages of hot' pressing. It should be noted thatthis is not a drying operation, as drying is not essential, althoughsome drying may take place unavoidably or even intentionally, as thepanels can be turned out at any desired moisture content by controllingthe humidity in the heating apparatus. Obviously, moisture may be add edto the panel if desired. Such control of moisture. content isimpractical to realize with the hot press. The purpose of the heating"is to increase the water resistance, and weather proofness.

A typical procedure inheating is as follows: Time 15 minutes, andtemperature 300 F. These panels gave the following results expressed inpounds per square inch shear strength:

Before After heating heating Dry strength 283 304 Wet strength 243 318 Ifind that considerable amounts of proteins, such as casein or isolatedvegetable proteins, can be admixed with the blood and the combinationbase then subjected to the same chemical treat These added proicecottonseed, castor, etc., also I include in this class i ofalkali-dispersibles. and may be used instead of casein or the isolatedproteins or used with these materials. On the other hand, if thealkalidispersible proteins are usedv without 'blood in my process, theygive considerable lower results as far as wet strength is concerned. Thecombination of some substantial amount, at least 10% of the glue base,of blood appears necessary in my. process. Although thealkali-dispersibles by themselves do not give good results in myprocess, they can be mixed with blood in large proportions, up to 90% ofthe glue' base, and still obtain many of the benefits of my process.

With certi n woods, for example, birch, I find that the chemicaltreatment of blood alone as described herein; is not sufficient to givethe requisite dry strength for some purposes with cold pressing. Onsuchwoods, I have found that 'I can incorporate a protein such as casein, orisolated vegetable proteins, or both, with the blood;

and then treat the combintion base with the same chemical treatment asdescribed above, and can obtain a glue better suited for these woodswith my process. I have found good results with mixtures of 10% bloodand 90% casein or chemically isolated protein with birch.

A typical formula is as follows:

Parts II. Blood 50 Terpineol 1 Casein 50 Lime 7 NaOI-I 10 Silicate 30'Water 460 Spread on birch wood, cold pressed, then heated to 220 F thisgave the following results in Dry Wet Soya bean protein can besubstituted for casein in the above formula although more water must beadded, which in this process, is not a detriment. Also, the thinningtendency of soya bean protein is counteracted in this mixture.

It will be noted that my process so far has been intended to furnishplywood of maximum water resistance, as well as high, dry strength.However, it will be seen by the above results that even without theafter heating it gives very good results, and this is true on a numberof diiferent woods. I may therefore stop short of the heating step andproduce a thoroughly commercial plywood, especially where waterresistance of the very highest order is not desired.

I have also found that the various seed flours may be admixed witheither blood alone, or even with the combinations, blood-casein orblood-isolated vegetable protein, and may be thus used to constitute aconsiderable percentage, even seventy-five percent of the base of theglue used in my process, so long as blood constitutes 10% of the base.The glue made from such admixture has advantages in working properties,in particular, it tends to lump very much less than the glue does madewithout the seed flours. Also, the viscosity and consistency-of the gluemade by admixture of seed flours is much more constant with time. I haveused amounts of seed flours up to 75% of the base and find that myprocess can be effectively carried out with such an adhesive. The amountwhich I use varies with different woods. For example, on fir I find thata mixture of 50 parts of soya bean fiour with 50 parts of blood givesexcellent results. By thus using these considerable amounts of seedfiours, I am enabled to make a much more economical adhesive for use inmy process and at the same time realize all the necessary requirementsto fit into my process. In fact, I find that although casein givesrelatively inferior wet strength when used alone as the glue base in myprocess, yet a glue made from a mixture of 50 parts casein and 50 partsblood as a base, gives much better wet strength than is obtained withblood alone.

When using seed flours admixed, I use substantially the same chemicaltreatment as specified for the blood. The use of caustic soda as such isparticularly desirable with seed fiour combinations.

Typical formulae of such seed flour-blood glues are as follows:

the highly water resistant result I have described will not be realized.I have experimented with many agents in an endeavor to find one whichwill eliminate the foam and I find that the terpineols are particularlyeifective in this respect on this particular glue. Instead of using pureterpineol, I may also use, for example, pine oilwhich contains terpineolin a considerable percentage and there are also other oils of likenature which contain terpineol, all of which I consider as equivalentsfor this step of my method. I find that 2% of terpineol on the basis ofthe glue base gives good practical Working results.

Plywood made from my process and using the glue made as above described,is characterized by a remarkable absence of foam. It has been known fora long time that blood glues were particularly liable to foam and whilea water resistant plywood was obtained by prior known glues 'when hotpressed, yet the water resistance of such hot pressed blood plywoodsufiered considerably because of the foam in the glue. To obtain thehighest water resistant plywood, it is essential that foam be eliminatedas completely as possible. This I have succeeded in doing by the use ofterpineol as described above. The result is that I get a plywood whichis characterized by absence of any evidence of foam onthe glue line andit is this homogeneous glue line which contributes in a large measure tothe highly water resistant results or even waterproof results that Ihave obtained.

I have found that a convenient and efficient way to use terpineol is toadd it to the dry glue base. I have found that it can be stored with thedry glue base for a long period of time without losing its effectivenessand without afiecting objectionably the glue base. It is also effectivewhen added at any other point in the mixing operation of producing thefinished glue. I have also found that terpineol increases to some extentthe water resistance of the glue.

I have found the following procedure a convenient method of preparing myglue for use in my process:

Add the dry adhesive base, whether it be blood alone or mixture of bloodand alkali-dispersibles, to a portion of the water to be used. By addingthe dry adhesive to the water slowly and by efiicient mixing, lumpingcan be avoided and a smooth mixture obtained. The chemicals such aslime, caustic soda and sodium silicate are then added to this mixture insolution or suspension in water, and mixed in thoroughly. Terpineol maybe added either to the dry glue base or to the wet glue mixture. Whenthe right amount of water is added to give the glue a suitableconsistency for spreading, the glue is ready for use.

H P Unheated fir Heated fir Soyaempea I bean seed nut Casein Blood Limeg gg g 2% Water I flour flour flour Dry Wet Dry Wet All of the gluesabove described tend to foam considerably in the spreader. In order tomake the highly resistant plywood that I have described, it isparticularly essential that this foam be eliminated or kept at aminimum. Otherwise, a sufiicient spread can not be obtained, and

A typical mixing formula follows:

VII. To 135 lbs. of water, add 100 lbs. of a mixture of parts soya beanflour and 50 parts blood and 2 parts of alpha terpineol, stir 10minutes, add 330 lbs. of water, stir 2 minutes, add 7 lbs. of limesuspended in 25 lbs. of water; stir 1min- 'ute, add 8 lbs. of causticsoda dissolved in lbs.

of water, stir 1 minute, add lbs. of water glass,

soda, a considerable amount of water. can be used in the glue, and stillmaintain a. spreadable consistency, thus affording an economical glue touse. Also, the use of caustic soda gives the high dry strength needed inmy process, whereas ammonium hydroxide, when used in'my process does notgive sufiicient dry strength. This in itself is a very unexpected resultfor it has commonly been found that the greater is the con centration ofthe glue solution, the greater is the strength of the bond obtainedtherefrom. Manu= facturers of glue when faced with the problem ofincreasing the strength of the bond to be obtained from any glue base,have heretofore striven to reduce the amount of water required to bringthe glue to a proper working consistency, for

it has been the common experience of workers in this. art thatconcentration of the glue solution tends to increase the strength of thebond, whereas dilution of the glue solution weakens the bond. obtained.It is therefore. a most unexpected and surprising thing to discoverthata. glue made bythe treatment of blood with considerable amounts ofcaustic soda, which requires about seven parts of water to one part ofblood in order to bring the glue to proper working consistency should becapable of giving a bond far superior in strength to that obtained withthe blood glues commonly in use which contain only comparativelymildly.alkaline reagents and are very concentrated, containing onlyabout 1 to 2 parts of water to each part of dry blood.

Blood glues made by heating during the mixing are quite different thanglues made without heat. Blood in the presence of water and heatcoagulates rapidly, and glues made hot have a higher water requirementthan glues made cold, but the adhesion suffers by the heating.

In hot pressing procedure, the usual procedure is to apply a thincoating. of blood glue and immediately place in hot press and applypressure.

'There is little lapse of timesothat the glue does not have opportunityto penetrate or dry out to any great extent. However, in cold pressing,considerable time in ordinary manufacturing procedure elapses betweenthe time of assembly and the time when pressure is applied. Hence 'therelatively large amount of glue base used in hot 1 pressing with bloodwould necessarily be increased by the step of cold pressing of myprocess. I overcame this objection by discovery that blood could betreated with a large percentage of chemicals which imparted a positivealkalinity and ing can be safely carried out not only without adverselyaflfecting strength, but, markedly increasing wetstrength. a

I may also use sodium silicate, that is, water glass, with caustic sodaand without lime. fI find that the silicate greatly increases the waterresistance of the glue. A typical formula with blood and sodium silicateis as follows:

1 Parts VIII. Dried blood 100 v Caustic soda 12 Sodium silicate 30 Water600-650 It is to .be understood that I do not confine myself to sodiumsLlicate, commonly known as waterglass, but may use other solublesilicates as well. I find also that sodium metasilicate can be used withblood in my process and give very good results. A typical formula withblood and sodium metasilicate is as follows: v

' Parts IX. Dried blood 100 Sodium metasilicate 42.5 Water 700- 750 Theconstruction unit resulting from the use of the glue and process hereinset forth may be identified by the physical and/or'chemical propertiesof the same.

The advantages of mypro'cess are:

1. That I am enabled to secure a highdegreecan be admixed, and stillrealize the benefits of heat treatment of blood.

5. On some woods, such as coniferous, thehot press is impracticalbecause of checking, etc; But I can secure all the benefits of thehot'press in my process, without its disadvantages, and with manypositive advantages, both in low cost and superior quality.

It is to be understood that I can'also use, blood that has been heatedin a dry state. I have found that dried blood can be heated totemperatures much higher than those at which the blood coagulatesin thepresence of moisture, without causing the dry blood to becomenon-dispersible in a1- kali. I have raised the temperature of dry bloodto 270 F. without causing it to become non-dispersible in alkalies. Ihave found that the heat treatment of blood is in many cases beneficialto the water resistance of the resulting glue.

By the term blood" I mean to include fresh blood as well as spray driedor film dried bloods, which have not been rendered non-disper'sible inalkaliesin'the drying. I also include blood from which fibrin has notbeen separated.

-A's equivalents ofcaustic soda, I include potas-.

sium hydroxide, but not ammonia; as equivalents of sodium salts thecorresponding potassium salts; as-equivalents of lime, baryta andstrontia. This of course includes caustic soda or potash developed bydouble decomposition-as described herein.

By glue I mean ordinary aqueous dispersed glue, spread wet.

By dry adhesive base I mean. dry blood mixture of dry blood and otherprotein containing material. When fresh blood is used I mean the solidcontents of such blood.

I claim:

1. A glue for use in a cold press comprising the reaction products inaqueous 'medium at normal temperature of blood treated with not lessthan approximately 3%, nor more than approximately 20% of causticalkali, said percentage being based upon the blood constituent.

2. A glue for use in a cold press comprising the reaction products inaqueous medium at normal temperature of blood treated with not less thanapproximately 3%, nor more than approximately 20% of caustic alkali; andhydrated lime, said percentage being based on the blood constituent.

3. A glue for use in a cold-press comprising the reaction products inaqueous medium at normal temperature of blood treated with not less thanapproximately 3%, nor more than approximately 20% of caustic alkali;hydrated lime; and sodium silicate, said percentage being based on theblood base, the step of treating blood with terpineolfor overcoming thefoaming tendency of blood glue.

7. A.glue for use in a cold press comprising the reaction products of abase consisting of not less than 10% blood, and not more than 90% of analkali-dispersible protein containing material, which base is acted uponin aqueous medium at normal temperature by not less than approximately3%, nor more than approximately 20% of caustic alkali, said percentagebeing based upon saidbase.

8. A glue for use in a cold press for plywood comprising the reactionproduct of a base consisting of not less than 10% blood and not morethan 90% of an alkali-dispersible protein containing material, whichbase is acted upon by not less than approximately 3%, nor more thanapproximately 20% of caustic alkali; hydrated lime; and sodium silicate,said percentage being based upon the said base 9. A glue for use in acold press for plywood consisting of the reaction product of a baseconsisting of not less than 10% blood and not more than 90% of analkali-dispersible protein containing material, which base is acted uponby not less than approximately 3%, nor more than approximately 20% ofcaustic alkali; hydrated lime; and sodium silicate, said percentagebeing based upon the said base.

10. A glue for use in a cold press for plywood comprising the reactionproducts of a base consisting of not less than 10% 01 blood and not morethan 90% of an alkali-dispersible protein containing material in aqueousmedium; which base is acted upon by not less than approximately 3%, normore than approximately 20% of caustic alkali; and terpineol. v

11. A glue for use in a cold press for plywood comprising the'reactionproducts of a. base consisting of not less than 10% of blood and notmore than 90% of soya bean flour, which base is acted upon in aqueousmedium at normal temperature by not less than approximately 3%, or morethan approximately 20% of caustic alkali, said percentage being basedupon said base.

12. A glue for use in a cold press for plywood comprising the reactionproducts of a base consisting of not less than 10% blood and not morethan 90% soya bean flour, which base is acted uponin aqueous medium atnormal temperature by not less than approximately 3%, nor more thanapproximately 20% of caustic alkali; and hydrated lime, said percentagebeing based upon said base.

13. A glue for use in a cold press for plywood comprising the reactionproducts of a base consisting of not less than 10% blood and not morethan 90% soya bean flour, which base is acted upon in aqueous medium atnormal temperature by not less than approximately 3%, nor more thanapproximately 20% of caustic alkali; hydrated lime; and sodium silicate,said percentage being based upon said base.

14. A glue for use in a cold press for plywood comprising the reactionproducts of not less than 10% blood and not more than 90% soya beanflour, which base is acted upon in an aqueous medium by not less thanapproximately 3%, nor more than approximately 20% of caustic alkali; andterpineol, said percentage being based upon the dry adhesive base.

15. An adhesive for use in a cold press comprising the reaction productsof blood acted upon in aqueous medium at normal temperature by 8%caustic soda, 7% lime and 30% silicate, said percentage being based uponthe blood constituent.-

16. An adhesive for use in a cold press comprising the reaction productsof blood acted upon in aqueous medium by 8% caustic soda, 7% lime, 30%silicate; and terpineol, said percentage being based upon the bloodconstituent.

17. A glue for use in a cold press comprising the reaction products ofblood and alkali-dispersible protein containing material acted upon inaqueous medium at normal temperature by i.

8% caustic soda, 7% lime, 30% silicate, said percentage being based uponthe dry adhesive base.

18. A glue for use in a cold press comprising the reaction products inan aqueous medium at normal temperature of 100 parts dried blood; 12parts caustic soda; 30 parts sodium silicate; and 600 to 650 partswater.

19. A glue for use in a cold press comprising the reaction products inan aqueous medium at normal temperature of'100 parts dried blood; 42.5parts sodium metasilicate; and 700 to 750 parts water.

20.. A glue for use in a cold press consisting of the reaction productsin an aqueous medium at normal temperature, of blood, and sodiummetasilicate.

21. A glue for use in a cold press comprising the reaction products, inan aqueous medium at normal temperature, of blood, sodium metasilicate,and caustic soda, the latter in the proportion of not less than 3% normore than 20% of the blood constituent.

22. A glue for use in a cold press consisting of the reaction products,in an aqueous medium at normal temperature, of blood, sodium silicate,and caustic soda, the latter in the proportion of not less than 3% normore than 20% of the blood constituent.

' CHARLES N. CONE.

